Ketene dimer sizing composition and process for sizing paper therewith



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KETENE DIR HER SIZING COMPOSITIGN AND PROCESS FOR IZING PAPER THEREWITH Cyrus A. Weisgerher, Chadds Ford, Pa., assignor to Hercuies Powder Company, Wilmington, DeL, a corporation of Delaware No Drawing. Application March 11, 1957 Serial No. 645,020

12 Claims. (Cl. 92-6) This invention relates to novel ketene dimer sizing compositions and to the use of same in the sizing of paper by internal addition as to the beater of a papermaking system.

One of the essential requirements for the internal addition of ketene dimers to pulp slurries is that the ketene dimer be finely enough divided to give uniform distribution in the pulp slurry and, therefore, sizing when the sheet is made. This is usually accomplished by mixing the ketene dimer with a nonionic emulsifying agent which makes it readily dispersible in water for the formation of aqueous emulsions. However, since these nonionic emulsions are not substantive to paper fibers, the retention of the ketene dimer by the fibers is not complete with the result that some of the material goes to waste with the discarded white water. Moreover, in order to avoid excessive packaging and shipping costs which would add to the cost of the product, these aqueous emulsions are generally prepared by the user.

An important object of the present invention, therefore, is the provision of a process for the internal sizing. of paper with ketene dimers which does not require the use of aqueous emulsions to obtain uniform distribution of the ketene dimer in aqueous pulp slurries.

Another object of the invention is the provision of a process for the internal sizing of paper with ketene dimers wherein improved retention of the ketene dimers by the paper fibers is obtained with resultant economies in operation.

Still another object of the invention is the provision of a ketene dimer sizing composition in the form of a freefiowing powder which may be economically packaged and shipped, which is readily dispersible in an aqueous pulp slurry without the need for addition of an emulsifying agent, and which may be used alone for the preparation of sized'paper or in conjunction with pigments, fillers and the like to provide papers which are both sized and coated or. filled. i

In accordance with the present invention, uniform distribution of finely-divided ketene dimers in aqueous pulp slurries, and improved retention and sizing, are obtained by (l) dispersing a ketene dimer or mixture of ketene dimers on a carrier comprising finely-divided amorphous silica to form a free-flowing powder in which the particles of silica contain a deposit or coating of the ketene dimer, (2) incorporating the finely-divided free-flowing powder into an aqueous pulp slurry, and (3) sheeting and drying the pulp in the conventional manner. 7

Some sizing of the paper by the ketene dimer will usually be developed during drying of the paper web in accordance with conventional drying procedures utilized in the art. If desired, the sheet may be cured by heating to a relatively elevated temperature, say about 100 C., for a short period of time such as about 10 minutes. However, this is not necessary as adequate sizing develops on mere standing or storage at room temperature for a day or two.

A ',805,743 Patented ec- 2j3, 1958 Having described the invention generally, the following examples are given in illustration but not in limitation of the invention. All parts and percentages are by weight unless otherwise specified.

EXAMPLE 1 Into a Waring Blendor was placed 10 parts of Hi-Sil 303, a purified low-density silica manufactured by Columbia-Southern Chemical Division of the Pittsburgh Plate Glass Company, having the following properties:

The Blendor vessel was warmed in a steam bath to about 50 C. and 10 parts of molten alkylketene dimer prepared from a mixture of myristie and palmitic acids (M. P. ca. 33 C.) was added dropwise to the vigorously agitated silica. When addition was complete, the solid that passed through a 275-mesh screen was used to size unbleached kraft pulp and bleached sulfite pulp by addition in the papennaking system at the size crock at pH 7.0. One-half part (0.5% dimer based on pulp) of the silica-dimer powder was added to 50 parts of pulp in two liters of water and stirred 5 minutes. After this time the mixture was diluted to 20 liters and handsheets weighing 2.5 parts were made in the usual manner utilizing a Noble and Wood handsheet machine. Twelve (12) successive sheets were made for each pulp and the water in which the first sheet was made was recycled for the preparation of the next sheet, and so on, until the series was completed. Sheets 1, 2, 3, 4 and 12 were then tested for sizing by determining resistance to ink penetration with the Hercules photometer. The results are set forth in Table 1 below.

It is significant that even the first sheet in each series was well and uniformly sized. The first sheet corresponds to a completely open papermaking system.

EXAMPLE 2 Equal portions of Hi-Sil 303 and an alkylketene dimer prepared from a mixture of stearic and palmitic acids were blended by mixing molten alkylketene dimer and silica in a ribbon blender and the blended material then passed through a Micronizer (air attrition mill). The resulting product was a free-flowing powder containing 5.0% by weight ketene dimer and having a particle size essentially that of the silica. The product was eva uated in a paper mill under the following conditions.

Three beaters were each furnished as follows:

Filler, sheet pulp and gum were mixed first in the beater and were followed by the ketene dimer sizing composition. The second and third heaters were not dumped until white water was available for dilution from running some of the pulp in beater No. 1. All the refining was done in two Jordan refiners in series. The sheet was given a starch surface treatment in a size press and then three trips in the calender.

Samples of the sheet which were not cured, together with corresponding samples which were cured minutes at 105 C., were evaluated for sizing at the end of 24 hours and the uncured samples were also evaluated at the end of 72 hours. The ink resistance, in seconds, as determined on the Hercules photometer using Standard Feather Ink-was as follows:

A ketene dimer sizing composition consisting of a freefiowing powder prepared as in Example 2 was evaluated in a paper mill in a 50% bleached kraft50% bleached sulfite pulp under the following conditions.

A total of 20 lbs. of the ketene dimer sizing composi tion was divided equally between two bcaters containing about 1000 lbs. of pulp each. After the beating cycle, the two heaters of stock were combined, refined in a Jordan refiner and run on the machine in the usual manner. The degree of sizing of the paper at various times as determined by the Hercules photometer using Standard Feather Ink is shown in Table 3 below.

Table 3 INK RESISTANCE IN SEC. AT VARIOUS TIMES In order to attain the objectives of the invention, the free-flowing powder constituting the ketene dimer sizing compositions utilized herein should have a ketene dimer content of at leastabout 20% by weight, and preferably at least about 42% by weight, based on the weight of the composition, and a particle size sufficiently small to obtain uniform distribution of the ketene dimer in the pulp slurry. These requirements necessarily place certain limitations on the carrier which may be employed particularly, and more importantly, with respect to particle size and oil absorption properties. Thus, it has been found that inorder to obtain uniform distribution of the ketene dimer throughout the aqueous pulp slurry, the

particle size should not exceed about 74 microns through a 270-mcsh screen) and preferably should be below about 44 microns (100% through a 325-mesh screen).

The oil absorption of the carrier must be relatively high to permit formulation of free-flowing powders containing 20% or more by weight of ketene dimer. This will usually require an oil absorption (linseed oil, rub-in meth 0d) of at least about 100 grams of oil per 100 grams of carrier and preferably at least about 200 grams of oil per 100 grams of carrier. The suitability of a particular carrier material from the standpoint of oil absorption characteristics may be determined by mixing known amounts of the carrier and liquid alkylketene dimer and determining the maximum amount of dimer that can be mixed with the carrier but yet have a free-flowing powder instead of a putty-like mass. If the required amount of ketene dimer, i. e., at least about 20% by weight based on the weight of the composition, cannot be added to form a freefiowing powder instead of a putty-like mass, the material is not suitable for purposes of the invention.

In addition to the indicated particle size and oil absorption characteristics, the silica utilIzed as the carrier should be amorphous, white and free of colored contaminating material, and have a pH in the range of about 2.5 to about 7.0, and preferably in the range of 3.5 to about 4.5, at 5% concentration in distilled water. The significance of the pH range is that it permits intimate mixing of the ketene dimer with the silica without causing excessive losses in activity due to hydrolysis of the dimer such as occur when alkaline materials are used.

A silica which is suitable for use herein may be prepared by reacting a finely-divided alkaline earth metal silicate with an aqueous solution of ammonium chloride in accordance with the process disclosed in British Patent No. 756.875. followed, if necessary, by treating a water slurry of the material with an acid such as hydrochloric, sulfuric or the like to reduce the pH to between 2.5 and 7.0 and preferably to between 3.5 and 4.5 at 5% concentration in distilled water, filtering and drying. However, any suitable method may be utilized which results in a material having the desired characteristics hereinabove described.

The ketene dimers which are used in the instant process are dimers having the formula ERCH=C=O1 where R is a hydrocarbon radical, such as alkyl having at least 8 carbon atoms, cycloalkyl having at least 6 carbon atoms, aryl, aralkyl and alkaryl. In naming ketene dimers, the radical R is named followed by ketene dimer. Thus, phenyl ketene dimer is:

benzyl ketene dimer is:

and decyl ketene dimer is: [C H CH=C=Ol Representative ketene dimers that may be used in the process of the instant invention include octyl, decyl, dodecyl, tetradecyl, hexadecyl, octadecyl, eicosyl, docosyl, tetracosyl, phenyl, benzyl, ,B-naphthyl and cyclohexyl ketene dimers, as well as the ketene dimers prepared from montanic acid, naphthenic acid, d -decylenic acid, A dodecylenic acid, palmitoleic acid, oleic acid, ricinoleic acid, petroselinic acid, vaccenic acid, linoleic acid, linolenic acid, eleostearic acid, licanic acid, parinaric acid, tariric acid, gadoleic acid, arachidonic acid, cetoleic acid, erucic acid and selacholeic acid, as well as ketene dimers prepared from naturally occurring mixtures of fatty acids, such as those mixtures found in coconut oil, babassu oil, palm kernel oil, palm oil, olive oil, peanut oil, rape oil, beef tallow, lard (leaf) and whale blubber. Mixtures of any of the above-named fatty acids with each other may also be used.

A preferred method of preparing the novel ketene dimer sizing compositions ofthe invention is "by passing the ketene dimer and" finely-divided silica: through an air attrition mill called a Micronizer. The materials may be introduced into the Micronizerin a mixed or blended form or separately.

In such a mill, the particles are givena swirling motion in a cylindrical chamber by'means of air jets positioned to discharge air into the chamber tangentially at a discharge pressure up to 100 lbs/sq. in. In this chamber the particles continually collide at high velocity so that any coalesced particles are broken up and the original fine particle size maintained, thus eliminating any need for subsequent classification of the particles. Simultaneously, the ketene dimer particles, it added separately, are deposited in and on the silica particles. As the treated silica particles reach the required finely-divided state which, in accordance with the invention is essentially the same as that of the untreated particles, they work downwardly centrally out of the container and are discharged through the bottom thereof ready for use.

While it is preferred, as indicated, to prepare the material in an air attrition mill, other methods of preparation such as mixing and/ or blending in a Waring Blendor or similar type of apparatus and mechanical equivalents of such mixing, blending and air attrition mills may be utilized. However, methods of preparation which involve the use of high temperatures such as spray-drying an aqueous mixture of the ingredients shouldbe avoided since (1) hi h temperatures cause hydrolysis of the ketene dimer thereby destroying or, at least substantially, impairing the sizing activity of the dimer and (2) spraydrying, as well as other types of drying aqueous mixtures, causes the particles to coalesce thereby destroying the fine state of subdivision of the material required to obtain uniform distribution of the ketene dimer in the pulp slurry. Moreover, aqueous systems require the use of an emulsifier which would be present in any product obtained to further decrease the level of sizing obtained, if any, as well as the rate of sizing development.

The ketene dimer sizing compositions, prepared as herein described, may be added to an aqueous pulp slurry as is, i. e., as a free-flowing powder or. dry solid or may be dispersed in water to form an aqueous slurry, if so required by continuous machine operation. In paper mill operation, the sizing compositions should be added to the stock before the refining steps to insure uniform distribution throughout the pulp slurry. The material may be used over the pH range of 4.5 to 9 but is preferably use-d in the pH range of 7-8.

The amount of sizing composition which should be added to the stock slurry to obtain a desired degree of sizing will vary depending on factors such as the ketene dimer content of the composition, the sizing desired, the type of ketene dimer, the type of stock and so on. The degree of retention of the material bythe cellulose fibers is also a factor to be considered for while retention is substantially better than that obtained with aqueous emulsions it is, of course, not complete.

In general, considering the various factors involved, the sizing compositions should be added to the stock slurry in amounts such that the concentration of ketene dimer present will be within the range from about 0.01% to about 1% and preferably within the range from about 0.1% to about 0.5% by weight based on the weight of the pulp. Depending on the conditions of treatment and the results desired, this may involve the addition of as little as about 0.05% and as much as about 5% by Weight of the sizing compositions based on the weight of the pulp. Usually, however, these sizing compositions will be added in amounts ranging from about 0.1% to about 1% by weight based on the weight of the pulp and this is the preferred range.

Operating Within the ranges specified above, a sized paper may be obtained containing such small quantities of noncelhzlosic material, i. e., silica, as to be classified ticularly effective for this purpose is Cato 8, a cationic starch (modified cornstarch having a nitrogen content of about 0.25%) produced and sold by National Starch Products Company. Thus, it has been found that when from about 0.1% to about 0.5% by weight, based on the weight of the pulp, of a cationic starch, such as Cato 8, is added to the stock slurry before, after or simultaneously with the sizing composition, a decided improvement in retention is obtained. The following example will serve to illustrate this phase of the invention.

EXAMPLE 4 A pulp mixture composed of 5 g. Weyerhaeuser bleached kraft pulp, 4 g. Puget Sound bleached sulfite pulp-and 3.5 g. Astracel, a bleached kraft pulp,.was beaten for 20 minutes in 500 ml. of water in a Waring Blender with 0.0625 g. (0.5% based on pulp) of a sizing composition consisting of ketene dimer supported on Hi-Sil 303. The ketene dimer was prepared fro-m a mixture of palmitic and stearic acids and the weight ratio of ketene dimer to Hi-Sil 303 was 1:1. The mixture was cooled during heating.

After beating, the pulp was diluted with 4 liters of water and 6.2 ml. of 1% Cato 8 (0.5% Cato 8 based on pulp) solution was added. After stirring one minute, 275ml. aliquots of the diluted pulp slurry were removed to make five successive sheets 5 inches in diameter. Befor sheeting each portion of pulp was diluted with 250 ml. of water. Water filtered from one sheet was used for diluting the succeeding sheet. After cur ing for 15 minutes at a temperature of 105 C., the following ink resistance was observed on the Hercules photometer using Standard Feather ink and an end point of reflectance.

The sizing obtained in the above example is markedly superior to that obtained with the same pulp mixture and sizing composition but without the use of Cato 8.

it will thus be seen that the present invention provides an improved dimer sizing composition and method for the internal sizing of paper. These sizing compositions may be used for the internal sizing of paper without the need for emulsification, thereby eliminating the problem of emulsion quality. By utilizing the compositions of the invention, improved retention and sizing are obtained as compared with the use of aqueous emulsions. MoreoverQthe compositions may be economically packaged and shipped and do not deteriorate on storage any faster than alkylketene dimers alone. While preferred embodiments of the invention have been specifically described herein, the invention is not to be construed as limited thereby except as tne same may be included the following claims.

What I claim and desire to protect by Letters Patent is:

l. A composition adapted to impart sizing to paper comprising a free-flowing powder made up of finely-divided silica particles having a deposit thereon of a ketene dimer, said composition having a particle size not in ,1? excess of about 74 microns, and said ketene dimer having the formula [RCH=C=O] where R is a hydrocarbon radical, such as alkyl having at least 8 carbon atoms, cycloalkyl having at least 6 carbon atoms, aryl, aralkyl and alkaryl.

2. A composition in accordance with claim 1 containing at least about 20% of ketene dimer by weight based on the weight of the composition.

3. A composition in accordance with claim 2 wherein the finely-divided silica has a linseed oil absorption of at least about 100 grams of oil per 100 grams of silica.

4. A composition in accordance with claim 3 wherein the finely-divided silica has a pH from about 2.5 to about 7.0 at 5% concentration in distilled water.

5. The process of preparing a composition adapted to impart sizing to paper which comprises treating finelydivided silica with ketene dimer to form a tree-flowing powder containing finely-divided silica particles carrying deposits of ketene dimer thereon, said silica particles having a particle size not in excess or" 74 microns, and said ketene dimer having the formula [RCH=C=O] where R is a hydrocarbon radical, such as alkyl having at least 8 carbon atoms, cycloalkyl having at least 6 carbon atoms, aryl, aralkyl and alkaryl.

6. The process of preparing a composition adapted to impart sizing to paper which comprises mixing finelydivided silica and ketene dimer in gaseous media to form a free-flowing powder containing finely-divided silica particles carrying deposits of ketene dimer thereon, said particles having a particle size not in excess of about 74 microns, said free-flowing powder containing at least about 20% by weight of ketene dimer based on the weight of the composition, said ketene dimer having the formula IRCH=C=O1 where R is a hydrocarbon radical, such as alkyl having at least 8 carbon atoms, cycloalkyl having at least 6 carbon atoms, aryl, aralkyl and alkaryl.

7. The process of preparing a composition adapted to impart sizing to paper which comprises subjecting a mixture of finely-divided silica and ketene dimer to air mixing to form a free-flowing powder containing finelydivided silica particles carrying deposits of ketene dimer thereon, said particles having a particle size not in excess of about 74 microns, said free-flowing powder containing at least about 20% by weight of ketene dimer based on the weight of the composition, said ketene dimer 8 having the formula ERCH=C=O1 where Ris a hydrocarbon radical, such as alkyl having at least 8 carbon atoms, cycloalkyl having at least 6 carbon atoms, aryl, aralkyl and alkaryl.

8. The process of sizing paper which comprises forming an aqueous suspension of paper pulp, incorporating in the aqueous suspension 8. sizing composition comprising a free-flowing powder made up of finely-divided silica particles having deposited thereon a lretene dimer, said coated particles having a particle size not in excess of about 74 microns, said ketene dimer having the formula IRCH=C=O1 where R is a hydrocarbon radical, such as alkyl having at least 8 carbon atoms, cycloalkyl having at least 6 carbon atoms, aryl, aralkyl and alkaryl, then forming the aqueous suspension into sheets.

9. A process of sizing paper in accordance with claim 8 wherein the ketene dimer content of the sizing composition is at least about 20% by weight based on the weight of the composition.

10. A process of sizing paper in accordance with claim 9 wherein the sizing composition is added to the aqueous suspension of paper pulp in the form of a free-flowing powder.

11. A process of sizing paper in accordance with claim 9 wherein the sizing composition is added to the aqueous suspension of paper pulp in the form of an aqueous slurry.

12. Paper sized with from about 0.05% to about 5% of a sizing composition comprising ketene dimer supported on finely-divided silica, said sizing composition having a particle size not in excess of 74 microns, said ketene dimer constituting at least about 20% of said composition and having the formula [RCH=C=O] where R is a hydrocarbon radical, such as alkyl having at least 8 carbon atoms, cycloalkyl having at least 6 carbon atoms, aryl, aralkyl and alkaryl.

References (Zited in the file of this patent UNITED STATES PATENTS 2,510,661 Sattord June 6, 1950 2,627,477 Downey Feb. 3, 1953 2,706,163 Fitko Apr. 12, 1955 2,728,732 Arnett et al Dec. 27, 1955 2,762,270 Keim et al. Sept. 11, 1956 2,776,226 Hart Jan. 1, 1957 

8. THE PROCESS OF SIZING PAPER WHICH COMPRISES FORM ING AN AQUEOUS SUSPENSION OF PAPER PULP, INCORPORATING IN THE AQUEOUS SUSPENSION A SIZING COMPOSITION COMPRISING A FREE-FLOWING POWDER MADE UP OF FINELY-DIVIDED SILICA PARTICLES HAVING DEPOSITED THEREON A KETENE DIMER, SAID COATED PARTICLES HAVING A PARTICLE SIZE NOT IN EXCESS OF ABOUT 74 MICRONS, SAID KETENE DIMER HAVING THE FORMULA (RCH=C=O)2 WHERE R IS A HYDROCARBON RADICAL, SUCH AS ALKYL HAVING AT LEAST 8 CARBON ATOMS, CYCLOALKYL HAVING AT LEAST 6 CARBON ATOMS, ARYL, ARALKYL AND ALKARYL, AND THEN FORMING THE AQUEOUS SUSPENSION INTO SHEETS. 